1. Field of the Invention
The present invention is directed to a traffic control method for providing a predictive/guaranteed service which can be widely employed for an exchanger of various communication systems, such as ATM, PSTN and IMT-2000, and in particular to a traffic control method for efficiently controlling a predictive/guaranteed service which can guarantee a quality of service QOS by controlling a transmission route according to properties of various traffic data with a policing function using a moving ceiling MC function and a packet scheduling function using a first in first out FIFO or weighted fair queueing WFQ method.
2. Description of the Background Art
In general, multimedia traffics transmitted/received in a communication system include traffics requiring a real-time property and an existence property at the same time, such as a control signal and a signalling data, and multimedia traffics such as a video traffic and an audio traffic, in addition to simple data.
The above-mentioned traffics are all mingled and transmitted through a single physical transmission route, and thus it is necessary to develop a method for dividing and transmitting the traffics pursuant to their properties.
That is to say, different qualities of service QOS are required in relation to the multimedia traffics. Therefore, in order to effectively support the multimedia traffics, the transmission route should be properly controlled according to their properties, and then the traffics should be transmitted therethrough.
The multimedia traffics are divided into a guaranteed service, a predictive service and a best-effort service by a degree of the consumers"" satisfaction.
Here, in the case of the guaranteed service, the quality of service QOS should be satisfactory by 100%. A control-related data which should not lose a data falls under the guaranteed service. In the case of the predictive service, when a data is partially lost or a time is delayed, it can be restored. The audio traffic and video traffic are classified into the predictive service. The best-effort service implies a case that the quality of service QOS is not guaranteed and a data transmission is through a residual bandwidth.
The guaranteed service is required to completely satisfy the quality of service QOS. Thus, in order to guarantee it, an worst-case analysis should be carried out in relation to the performance of supported functions, and resources should be sufficiently assigned according to a result of the analysis.
Here, the worst-case analysis is performed by presuming that the traffics are driven at the same time, namely that each traffic is concentrated on a peak rate.
In the case of the predictive service, it should be considered to guarantee the quality of service QOS and to efficiently use the resources. That is, a necessary quality of service should be guaranteed by efficiently using a small volume of resources. It is not preferable to completely guarantee the quality of service QOS by consuming a large volume of resources.
On the other hand, in order to support the predictive/guaranteed service, intermediate nodes on a network should perform various functions, such as routing, resource reservation, call admission control, packet scheduling and policing. The routing, resource reservation and call admission control functions are necessary before calls are set, and the packet scheduling and policing functions are employed while a packet data is transmitted after the calls are set.
The packet scheduling function serves to determine on which input route a packet to be-transmitted next is positioned by operating in packet units, and to intercept the other input routes. The packet scheduling function supports a packet-level isolation.
Here, the policing function serves to observe each route whether packets are transmitted according to properties described in a traffic describer, and to control the route which does not transmit the packets pursuant to the properties to abandon the packets.
A maximum transmission rate (interval between the packets) and an average transmission rate (a number of the packets averagely transmitted for a predetermined period) are mainly observed by the policing function. When observing the average transmission rate, the policing function determines after observation for a predetermined time, and supports a call-level isolation.
Here, the call-level isolation implies a case that, although one route transmission rate is temporarily increased, an average transmission rate of the other routes is not reduced. That is, the quality of service QOS is influenced not by a volume or pattern of packets transmitted through the other routes but by a volume or pattern of packets transmitted through its own route.
According to the conventional art, as illustrated in FIG. 1, a cell traffic control circuit and a method thereof (Patent Publication Gazette Heisei 8-79251) which was applied for registration on Aug. 30, 1994, includes: a cell detecting unit 12 for detecting an input of a cell on an input line, a kind of the inputted cell and a frame discriminator displayed on a corresponding cell; a traffic observing unit 16 computing a number of frames (n) which are being transmitted through an output line and a number of frames (m) which are being transmitted in a circuit by each band managing unit (w); a frame buffer unit 14 having a frame buffer with a plurality of sides for accumulating cells composing a corresponding frame in frame units when the frames are inputted over a predetermined maximum frame number; an empty frame buffer managing unit 15 for managing an empty frame buffer in the frame buffer unit 14; and a frame transmission control unit 13 for determining to accumulate the inputted cell in the frame buffer unit 14 or to transmit the cell through the output line. The frame transmission control unit 13 has a frame accumulation and registration table 13a with the frames which are being accumulated and a value of the band managing unit (w). When the band managing unit in which the inputted cell detected by the cell detecting unit 12 is included is registered on the frame accumulation and registration table 13a, the corresponding cell is accumulated in the frame buffer unit 14. When the cell is not registered thereon, if the corresponding inputted cell is an intermediate cell or final cell composing an information frame, the cell is transmitted to the output line. In the case that the cell is a first cell or single cell, it is determined by a predetermined determination rule whether the cell is transmitted to the output line or accumulated in the frame buffer unit 14.
According to the method for controlling the cell traffic, a number of the traffics which can be transmitted through the line is set to be a maximum frame number (N) which can be simultaneously transmitted. There are provided a unit for computing a number of the frames (n) which are being transmitted through the line and a buffer for accumulating the cells composing a corresponding frame when the frames are inputted over the maximum frame number. When the cell is a valid cell and a first cell or single cell composing the information frame, in case xe2x80x98nxe2x80x99 is smaller than xe2x80x98Nxe2x80x99 (n less than N) at the time of the cell arrival, a series of cells included in an identical frame to the corresponding cell are transmitted through the output line, and in case xe2x80x98nxe2x80x99 is equal to xe2x80x98Nxe2x80x99 (n=N), a series of cells included in an identical frame to the corresponding cell are accumulated in the buffer discriminating the frame. In relation to the frame accumulated in the buffer, the cell traffic on the output line is controlled within a predetermined range by reading the cell from the buffer unit and transmitting it through the line within the range of xe2x80x98nxe2x89xa6Nxe2x80x99 in the case that the input cell is not an invalid cell such as an empty cell, or the input cell is accumulated in the buffer and not transmitted through the output line.
The above-described conventional method relates to the policing function itself which abandons not the packets of the frames which starts to be transmitted but the packets of the frames which are not yet transmitted in the condition that the packets should be abandoned, in order to transmit the frames as many as possible under a given transmission bandwidth (average transmission rate).
According to the conventional art, both a case that many traffics are inputted and a case that few traffics are inputted are not considered and reflected to an window. That is to say, the conventional art merely to the case that many traffics are inputted.
In addition, there is another disadvantage of the conventional art in that it relates merely to the packet-level policing function in order to effectively carry out not the packet-level control but the frame-level transmission.
In order to overcome the disadvantages of the conventional art, the present invention serves to guarantee the quality of service QOS by using an policing function and a packet scheduling function.
It is therefore a primary object of the present invention to provide a traffic control method for providing a predictive service which can effectively control the predictive service by controlling transmission routes of various traffic data with a policing function using a moving ceiling MC method and a packet scheduling function using the first in first out FIFO method, in the condition that it is presumed that a proper amount of resources is assigned to calls.
It is another object of the present invention to provide a traffic control method for providing a guaranteed service which can effectively control the guaranteed service by controlling transmission routes of various traffic data with a policing function using a moving ceiling MC method and a packet scheduling function using an weighted fair queueing method WFQ, in the condition that it is presumed that calls are set to have a sufficient volume of resources.
In order to achieve the primary object of the present invention, there is provided a traffic control method for providing the predictive service, including the steps of: observing an average transmission rate of packet data inputted through each route by using the MC method; determining whether the packet data satisfies passing conditions of the MC method by a result of the observation; storing the packet data in an output buffer when the packet data satisfies the passing conditions thereof; storing the packet data in an empty space of a certain storing unit or abandoning the packet data when there is no empty space, in the case that the packet data does not satisfy the passing conditions of the MC method; and transmitting the packet data to a receiving side through a single transmission route after detecting the output buffers of each route by a scheduler of the FIFO method and multiplexing the packet data in an input order.
In order to achieve another object of the present invention, there is provided a traffic control method for providing the guaranteed service, including the steps of: observing an average transmission rate of packet data inputted through each route by using the MC method; determining whether the packet data satisfies passing conditions of the MC method by a result of observation; carrying out a packet scheduling on the packet data on each route according to the WFQ method when the packet data satisfies the passing conditions thereof; storing the packet data in an empty space of a certain storing unit or abandoning the packet data when there is no empty space, in the case that the packet data does not satisfy the passing conditions; determining whether the packet can be currently serviced pursuant to weight conditions provided to each input route by the WFQ method; multiplexing and transmitting the packet data to a receiving side through a single transmission route when the packet can be currently serviced; and carrying out the packet scheduling on the packet data according to the WFQ method when the packet cannot be currently serviced.